Arc recovery with over-voltage protection for plasma-chamber power supplies

ABSTRACT

A system and method for managing power delivered to a processing chamber is described. In one embodiment current is drawn away from the plasma processing chamber while initiating an application of power to the plasma processing chamber during an initial period of time, the amount of current being drawn away decreasing during the initial period of time so as to increase the amount of power applied to the plasma processing chamber during the initial period of time.

PRIORITY

The present application claims priority to U.S. Provisional PatentApplication No. 61/120,250 entitled ARC RECOVERY WITH OVER-VOLTAGEPROTECTION FOR PLASMA-CHAMBER POWER SUPPLIES, filed Dec. 5, 2008.

FIELD OF THE INVENTION

This invention relates generally to power supplies for plasma processingapplications, and more particularly to systems and methods to manage theapplication of power therein.

BACKGROUND OF THE INVENTION

In plasma processing applications, arcs are known to develop when adischarge occurs between a point on a cathode where charge hasaccumulated and a point on the anode. If not extinguished quickly, arcscan be very detrimental to the process and the quality of the processedfilm.

To reduce energy supplied into an arc, many power supplies divert energyfrom the arc and circulate the energy within energy storing componentsof the power supply for a period of time in order to extinguish theplasma arc. After the plasma arc is extinguished, however, the energycirculated within the power supply can cause, for example, anover-voltage condition that can damage the power supply and/or plasmachamber if the energy is released to the plasma chamber. Also this highvoltage may lead to another arc.

Although present devices are functional for many applications, they arenot sufficient for many implementations or are otherwise satisfactory.Accordingly, a system and method are needed to address the shortfalls ofpresent technology and to provide other new and innovative features.

SUMMARY OF THE INVENTION

Exemplary embodiments of the present invention that are shown in thedrawings are summarized below. These and other embodiments are morefully described in the Detailed Description section. It is to beunderstood, however, that there is no intention to limit the inventionto the forms described in this Summary of the Invention or in theDetailed Description. One skilled in the art can recognize that thereare numerous modifications, equivalents and alternative constructionsthat fall within the spirit and scope of the invention as expressed inthe claims.

Embodiments of the present invention can provide a system and method forsupplying energy a processing chamber. In one exemplary embodiment,current is drawn away from the plasma processing chamber whileinitiating an application of power to the plasma processing chamberduring an initial period of time, the amount of current being drawn awaydecreasing during the initial period of time so as to increase theamount of power applied to the plasma processing chamber during theinitial period of time. And in some variations, the current that isdrawn away from the plasma processing chamber is converted to storedenergy and discharged.

Another embodiment may be characterized as an apparatus for supplyingenergy to a plasma processing chamber. The apparatus in this embodimentincludes an input terminal adapted to receive power that is generated bya power supply; an output terminal configured to apply the powergenerated by a power supply so that the power may be utilized by aplasma processing chamber; an energy diversion component configured todraw a decreasing amount of energy away from the output terminal so thatthe output terminal is capable of gradually increasing a level of energyfrom a low level of energy that is insufficient to ignite the plasma inthe plasma processing chamber to a level sufficient to ignite plasma inthe plasma processing chamber; and an energy discharge componentconfigured to draw energy away from the energy diversion component so asenable the energy diversion component to draw more energy away from theoutput terminal.

As previously stated, the above-described embodiments andimplementations are for illustration purposes only. Numerous otherembodiments, implementations, and details of the invention are easilyrecognized by those of skill in the art from the following descriptionsand claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Various objects and advantages and a more complete understanding of thepresent invention are apparent and more readily appreciated by referenceto the following Detailed Description and to the appended claims whentaken in conjunction with the accompanying Drawings wherein:

FIG. 1 is a block diagram depicting an exemplary embodiment of theinvention;

FIG. 2 is a block diagram depicting another exemplary embodiment of theinvention;

FIG. 3 is a schematic diagram depicting an embodiment of the arcrecovery components depicted in FIGS. 1 and 2;

FIG. 4 is a schematic diagram depicting an exemplary embodiment of arecovery/arc management component that may utilized to implement therecovery component and arc management component depicted in FIG. 1;

FIG. 5 is a flowchart depicting a method in accordance with manyembodiments;

FIG. 6A is a graph depicting voltage that is applied to a plasma chamberas a function of time in accordance with many embodiments;

FIG. 6B is a graph depicting plasma current as a function of time inaccordance with many embodiments;

FIG. 6C is a graph depicting current that is redirected away from aplasma chamber as a function of time in accordance with many modes ofoperation;

FIG. 6D is a graph depicting current that is output, as a function oftime, from the power module depicted in FIG. 1 and the power supplydepicted in FIG. 2;

FIG. 6E is a graph depicting a voltage at the node Vc described withreference to FIGS. 3 and 4.

DETAILED DESCRIPTION

Referring now to the drawings, where like or similar elements aredesignated with identical reference numerals throughout the severalviews, and referring in particular to FIG. 1, it illustrates is a blockdiagram 100 depicting an exemplary embodiment of the invention. Shown isa power supply unit 102 that is connected to a plasma chamber 104 with asupply cable 120. As depicted, the power supply unit 102 includes apower module 108 that is connected to a recovery component 110 and anarc management component 112, which is coupled to the supply cable 120.As shown, the recovery component 110 in this embodiment includes acontrol portion 132, an energy diverter 134, and a discharge regulator136. Also depicted is a control module 122 that is connected to thepower module 108, the recovery component 110, and the arc managementmodule 112.

The illustrated arrangement of these components is logical, theconnections between the various components are exemplary only, and thedepiction of this embodiment is not meant to be an actual hardwarediagram; thus, the components can be combined or further separated in anactual implementation, and the components can be connected in a varietyof ways without changing the basic operation of the system. For example,the recovery component 110 of the power supply unit 102 is divided intothree functional components in the exemplary embodiment, but thefunctions of these components could be subdivided, grouped together,deleted and/or supplemented so that more or less components can beutilized in any particular implementation. As another example, thefunctionality of the control module 122 and control portion 132 (whichmay be realized by hardware, firmware, software, or a combinationthereof) may be combined or further distributed.

Thus, the power supply unit 102, power module 108, recovery component110, arc management component 112, and control module 122 can beembodied in several forms other than the one illustrated in FIG. 1.Moreover, in light of this specification, the construction of eachindividual component is well-known to those of skill in the art.

In many embodiments, the power module 108 is a switching power supplythat is configured to provide a voltage (e.g., a DC voltage) at asufficient level to ignite and sustain a plasma that is contained in theplasma chamber 104. The plasma is generally used to process a work piecethat is not shown but is well known to those skilled in the art. In oneembodiment the power module 108 is configured in accordance with a bucktopology, but this is certainly not required and in other embodimentsthe power module 108 may include any other viable power supply topology.As shown, the power module 108 provides a negative voltage via a firstline 118 and a positive voltage via a second line 120.

The cable 120 is depicted as a single pair of conductors for simplicity,but in many embodiments the cable 120 is realized by a collection oftwo-conductor coaxial cables that connect the power supply unit 102 withthe plasma chamber 104. And in other embodiments, the cable 120 isimplemented with one or more twisted-pair cables. In yet otherembodiments the cable 120 may be realized by any network of cable,including, but not certainly not limited to, a simple conductor hookupand quadrapole connections.

In general, the arc management component 112 in the exemplary embodimentis configured to prevent arcs from occurring in the first place and/orextinguish arcs that occur within the 104 plasma chamber. In someembodiments for example, the arc management component 112 is configuredto detect arcs in the chamber 104, and in response to a detected arc,shunt current away from the plasma chamber 104.

The recovery component 110 generally operates to manage an applicationof power to the plasma chamber 104 after power to the chamber has beenreduced. For example, the recovery component 110 may be used to managean application of power to the chamber 104 during recovery from an arcevent (e.g., after the arc management component 112 has extinguished anarc) or when the power supply unit 102 is initially started after aperiod of being shut-down.

As depicted, the recovery component 110 in this embodiment includes anenergy diversion component 134 (also referred to herein as an energydiverter 134) that is configured (e.g., upon recovery from an arcmanagement event or upon startup of the supply unit 102) to draw adecreasing amount of energy away from the plasma processing chamber 104so as to increase a level of energy from a low level of energy (e.g., alevel of energy that is insufficient to ignite the plasma) to a levelsufficient to ignite plasma in the plasma processing chamber 104. Inmany variations, the decreasing amount of energy that is drawn away fromthe plasma chamber 104 limits a rate of change of voltage that isapplied to the chamber 104, which reduces the possibility of an arcbeing generated in the plasma and/or potentially damaging voltage levels(e.g., voltage levels that would damage components of the supply unit102).

The discharge component 136 (also referred to herein as a dischargeregulator 136) is generally configured to draw energy away from theenergy diversion component 134 so as enable the energy diversioncomponent 134 to draw more energy away from the plasma chamber 104. Thecontrol component 132 is configured to control the operation of thedischarge component 136 and the energy diversion component 134.

The control module 122 in this embodiment is configured to control oneor more aspects of the power module 108, recovery component 110, and thearc management component 112. For example, during a first mode ofoperation, the control module 122 allows the power module 108 to applypower to output terminals of the power supply unit 102, and during asecond mode of operation (e.g., in response to an arc being detected ora periodic clock signal), the control module 122 in this embodimenttemporarily deactivates the power module 108 and prompts the arcmanagement module 112 to extinguish the arc. And during a recovery modeof operation, the control module 122 activates the power module 108 andthe recovery component 110 to reapply power to the chamber 104.

As depicted in FIG. 1, the recovery component 110 and arc managementcomponent 112 in many embodiments are integrated within the power supply102 (e.g., within the same housing), but this is certainly not required,and as shown in FIG. 2, a recovery component in other embodiments may beadded as part of an accessory 210 (e.g., as a retrofit) to an existingpower supply 202 (e.g., a power supply that includes arc managementfunctionality.

Referring next to FIG. 3, shown is a schematic diagram 300 of anexemplary embodiment of the recovery component described with referenceto FIGS. 1 and 2. In this embodiment, the energy diverters depicted inFIGS. 1 and 2 are realized by a switch S1, a diode D2, and capacitor C1,which collectively form a current diversion path, and the dischargeregulator depicted in FIGS. 1 and 2 are realized by diode D1 andinductor L1. As shown, the switch S1 (e.g., an insulated gate bipolartransistor (IGBT)) is configured to turn on (e.g., responsive to acontrol signal from the control component 132) to activate the recoverycomponent 310. When the switch S1 is closed, output current from thepower supply 102, 202 is redirected away from the plasma chamber 104,through diode D2, to capacitor C1 and as a consequence, the rise of thevoltage that is applied by the recovery component 310 (and hence appliedby the power supply 102, 202) to the plasma is gradual.

When implemented with the power module 108 or power supply 202 describedwith reference to FIGS. 1 and 2, respectively, a resonant circuit isformed including an output inductance L_(O) of the power module 108 orpower supply 202 and the capacitance C1. And the capacitor voltage,VC1(t), can be characterized as:

${v_{C\; 1}(t)} = {{V_{C\; 0}{\cos\left( {\omega_{s}t} \right)}} + {I_{0}\sqrt{\frac{L_{0}}{C_{1}}}{\sin\left( {\omega_{s}t} \right)}}}$while the output inductor current, iL_(O)(t), can be calculated as:

${i_{L_{O}}(t)} = {{V_{C\; 0}\sqrt{\frac{C_{1}}{L_{0}}}{\sin\left( {\omega_{s}t} \right)}} + {I_{0}{\cos\left( {\omega_{s}t} \right)}}}$Where: L₀ is the power module or power supply output inductance; C1 isthe capacitor; ω_(s) is the resonant frequency; and I₀ is the outputinductor current at the end of an arc shutdown time.

In operation, when the recovery component 310 is initiated (e.g., byclosing S1), plasma voltage (Vout) and plasma current (Iplasma)gradually increases. This slow voltage rise allows plasma to developwithout having an overvoltage condition and the plasma will start takingcurrent from the power supply (the slope of the voltage can be adjustedby selection of the capacitor value for C1). In many modes of operation,once the plasma current becomes substantially equal to the supplycurrent (e.g., lout from the power module 108 or power supply 202), theovervoltage circuit is turned off, by turning off the recovery component(e.g., by opening S1).

When the switch S1 is open (e.g., when Iplasma is at a level associatedwith typical plasma processing), the capacitor C1 will discharge somestored energy through inductor L1. And the capacitor may also dischargemuch more energy through the inductor L1 during arc shutdown, when anoutput of the recovery component 310 may be shorted. One of ordinaryskill in light if this specification will appreciate that L1 can bechosen to regulate how much the capacitor C1 needs to be discharged inorder to provide optimal re-start after arc shutdown.

Referring next to FIG. 4, an exemplary embodiment of an arc recovery/arcmanagement component is depicted. In this embodiment the recoverycomponent 110 and arc management component 112 described with referenceto FIG. 1 share common components (e.g., switch S1 in this embodiment isa component of both the recovery component 110 and the arc managementcomponent 112). It should be recognized that this embodiment is merelyexemplary and that the recovery component in other embodiments isrealized as a separate component from the arc management component.

As shown, in this embodiment both switches S1 and S2 first turn on foran arc-shutdown event (e.g., responsive to a detected arc or to preemptan arc) and operate to re-direct output current away from plasma chamberthrough switches S1 and S2. Once arc shutdown is over, switch S2 opensand switch S1 remains closed, as described above with reference to FIG.3, to carry out a recovery mode of operation. Specifically, after S2 isopened (and S1 remains closed) plasma voltage and plasma currentgradually increase, which allows the plasma to develop withoutovervoltage and the plasma will start taking current from the powersupply. Once plasma current becomes substantially equal to the supplycurrent, the recovery portion of the recovery/arc management componentcan be turned off by opening S1.

The switches S1 and S2 in some embodiments are realized by an insulatedgate bipolar transistors (IGBTs), and in other embodiments is a fieldeffect transistor (FET). In yet other embodiments the series switches S1and S2 may be implemented by an integrated gate commutated thyristor(IGCT), a metal-oxide semiconductor-controlled thyristor (MCT), abipolar switch, or silicon-controlled rectifier. The diodes D1, D2 inthe exemplary embodiments may be realized by fast recovery diodes.

Referring next to FIG. 5, it is a flowchart depicting an exemplarymethod that may be carried out in connection with the embodimentsdescribed herein. While referring to FIG. 5, simultaneous reference willbe made to FIGS. 6A-6E, which respectively depict, as a function oftime, voltage applied to the plasma chamber; plasma current; currentthat is drawn away from the plasma chamber; current output from a powermodule (e.g., power module 108) or power supply (e.g., power supply202); and capacitor voltage Vc (described with reference to FIGS. 3 and4).

As shown, responsive to an arc being detected in a plasma processingchamber (Block 502), the arc is extinguished (Block 504). Referring toFIGS. 6A and 6B, for example, just after a time t₀, a drop in voltage atVout (e.g., the voltage applied to the plasma chamber) and rise in theplasma current indicates the presence of an arc, and in response, an arcmanagement component (e.g., arc management component 112) operates toreduce a level of current provided to the plasma.

As discussed with reference to FIG. 4, for example, both switches S1 andS2 of the recovery/arc management module close for an arc-shutdown eventand operate to re-direct output current away from plasma chamber plasmacurrent. Once the arc is extinguished, an application of power isinitiated to the plasma processing chamber (e.g., by power supply 102),and current is drawn away from the plasma processing chamber (e.g., by acurrent path formed by switch S1, D2 and C1 described with reference toFIGS. 3 and 4) while initiating the application of power to the plasmaprocessing chamber (Block 506). As shown in FIGS. 6A and 6B, at a timet₁ the arc is extinguished, and at a time t₂ arc recovery begins and anapplication of power to the plasma chamber is initiated. In addition, asdepicted in FIG. 6C, diversion current is simultaneously drawn away fromthe plasma chamber at the time t₂ (e.g., through the path formed byswitch S1, D2 and C1 described with reference to FIGS. 3 and 4).

As shown in FIG. 5, an amount of current that is being drawn away fromthe plasma processing chamber is decreased so as to increase the amountof power that is applied to the plasma processing chamber (Block 508).As shown in FIGS. 6A and 6B and, at time t₃, the voltage across theplasma is high enough so that the plasma current starts rising, and asdepicted in FIG. 6C the amount of current that is drawn away from theplasma chamber decreases during a time t₃ to t₄ so as to increase theamount of power that is applied to the processing chamber.

In particular, both the voltage Vout (depicted in FIG. 6A) and thecurrent plasma Iplasma (depicted in FIG. 6B) gradually rise while theamount of current that is redirected away from the plasma chamber(depicted in FIG. 6C) is decreased. Beneficially, The decreasing amountof energy that is drawn away from the plasma chamber limits a rate ofchange of voltage that is applied to the chamber, which reduces thepossibility of an arc being generated in the plasma and/or potentiallydamaging voltage levels (e.g., voltage levels that would damagecomponents of the supply unit 102, 202). At a time t₄, the current thatis redirected (depicted in FIG. 6C) is substantially zero, and theplasma current (depicted in FIG. 6B) and the current that is output fromthe power module (e.g., power module 108) or power supply (e.g., powersupply 202)(depicted in FIG. 6D) are substantially equal, and at thistime the recovery module may be disengaged (e.g., by opening S1).

In the exemplary method, the current that is drawn away from the plasmaprocessing chamber is converted to stored energy (e.g., by capacitor C1described with reference to FIGS. 3 and 4)(Block 510), and the storedenergy is discharged (e.g., by the inductor L1 described with referenceto FIGS. 3 and 4)(Block 512).

In conclusion, the present invention provides, among other things, asystem and method for managing the power provided to a plasma-processingchamber so as to prevent undesirable (e.g., damaging) voltage levels.Those skilled in the art can readily recognize that numerous variationsand substitutions may be made in the invention, its use and itsconfiguration to achieve substantially the same results as achieved bythe embodiments described herein. Accordingly, there is no intention tolimit the invention to the disclosed exemplary forms. Many variations,modifications and alternative constructions fall within the scope andspirit of the disclosed invention as expressed in the claims.

1. A system for supplying energy to a plasma processing chamber, thesystem comprising: a power supply; a plasma processing chamber coupledto the power supply via a first power line and a second power line; anarc management component configured to extinguish an arc in the plasmaprocessing chamber; and an arc recovery component configured to applypower to the plasma processing chamber after the arc has beenextinguished, the arc recovery component including: an energy diversioncomponent coupled by a switch across the first power line and the secondpower line to draw current away from the plasma processing chamber whilepower is applied to the plasma processing chamber during an initialperiod of time after the arc is extinguished, the amount of currentbeing drawn away decreasing during the initial period of time so as togradually increase an amount of power applied to the plasma processingchamber during the initial period of time; and a control component thatcontrols the switch to couple the energy diversion component across thefirst power line and the second power line during the initial period oftime after the arc is extinguished and decouple the energy diversioncomponent from being across the first power line and the second powerline after the initial period until another arc is detected.
 2. Thesystem of claim 1, wherein the arc recovery component includes an energydischarge component coupled to the energy diversion component, theenergy discharge component configured to discharge at least a portion ofthe energy that is diverted so as to enable the energy diversioncomponent to divert energy during a subsequent recovery cycle.
 3. Thesystem of claim 1, wherein the energy diversion component includes anenergy storage component, the energy storage component drawing thecurrent away from the plasma processing chamber and converting thecurrent that is drawn away into stored energy.
 4. The system of claim 3,wherein the arc recovery component includes an energy dischargecomponent coupled to the energy storage component, the energy dischargecomponent configured to discharge at least a portion of the storedenergy so as to enable the energy storage component to store additionalenergy.
 5. The system of claim 1, wherein the switch includes a switchselected from the group consisting of an insulated-gate bipolartransistor (IGBT), a metal oxide semiconductor field effect transistor(MOSFET), and a bipolar junction transistor (BJT), an integrated gatecommutated thyristor (IGCT), a metal-oxide semiconductor-controlledthyristor (MCT), a bipolar switch, or silicon-controlled rectifier. 6.The system of claim 1, wherein the arc management component includes theswitch and a second switch, the switch and the second switch are closedwhile the arc management component is extinguishing the arc so as toshunt current away from both the plasma processing chamber and theenergy diversion component.
 7. The system of claim 6, wherein the secondswitch is opened after the arc is extinguished and the first switch isopened after the initial period of time until another arc is detected.8. A method for supplying energy to a plasma processing chamber,comprising: detecting an arc in the plasma chamber; diverting,responsive to the detected arc, current away from the plasma processingchamber to extinguish the arc; placing a current diversion path acrossinputs to the plasma chamber in response to the arc being detected;drawing current away from the plasma processing chamber through thediversion path while initiating an application of power to the plasmaprocessing chamber during an initial period of time after the arc isextinguished, the amount of current being drawn away decreasing duringthe initial period of time so as to increase the amount of power appliedto the plasma processing chamber during the initial period of time;removing the current diversion path after the initial period of timeuntil another arc is detected; converting the current that is drawn awayfrom the plasma processing chamber to stored energy; and discharging thestored energy.
 9. The method of claim 8, including: increasing, duringthe initial period of time, an amount of voltage that is applied to theplasma processing chamber.
 10. The method of claim 8, wherein drawingcurrent away includes coupling the plasma processing chamber to anenergy storage element, the energy storage element drawing thedecreasing amount of current during the initial period of time.
 11. Themethod of claim 8, wherein discharging the stored energy includesdischarging the stored energy into at least one of the plasma processingchamber, a power supply that is applying power to the plasma processingchamber, or a resistor.
 12. An apparatus for supplying energy to aplasma processing chamber, comprising: an input terminal adapted toreceive power that is generated by a power supply; an output terminalconfigured to apply the power generated by a power supply so that thepower may be utilized by a plasma processing chamber; an energydiversion component configured to draw a decreasing amount of energyaway from the output terminal so that the output terminal is capable ofgradually increasing a level of energy from a low level of energy thatis insufficient to ignite the plasma in the plasma processing chamber toa level sufficient to ignite plasma in the plasma processing chamber; afirst switch disposed to couple the output terminal to the energydiversion component, the energy diversion component including acapacitor to draw current away from the output terminal and convert thecurrent to stored energy, the energy discharge component including aninductor configured to draw the stored energy from the capacitor so asto enable the capacitor to draw more current; a second switch disposedin series with the first switch, the series combination of the first andsecond switches creating, when the first and second switches are closed,a current path to shunt current away from the output terminal so as toextinguish an arc in the plasma processing chamber; and an energydischarge component configured to draw energy away from the energydiversion component so as enable the energy diversion component to drawmore energy away from the output terminal.
 13. The apparatus of claim12, including: a switch disposed between the output terminal and theenergy diversion component, the switch coupling the output terminal tothe energy diversion component so as to provide a current path betweenthe output terminal and the energy diversion component, the switch beingopen when current that is flowing from the output terminal to the plasmaprocessing chamber reaches a desired level.
 14. The apparatus of claim12, including: an arc management component configured to divert currentaway from the output terminal so as to extinguish an arc in the plasmaprocessing chamber, and when the arc is extinguished, to discontinue todivert current away from the output terminal; wherein the energydiversion component is configured, subsequent to the arc beingextinguished, to draw the decreasing amount of current away from theoutput terminal so as to gradually increase the amount of currentflowing from the output terminal to the plasma processing chamber afterthe arc is extinguished.
 15. The apparatus of claim 12, wherein thesecond switch is disposed in parallel with the capacitor so as to shuntcurrent away from the capacitor when the first and second switches areclosed, and once the arc is extinguished, the second switch is opened soas to enable the current to flow through the first switch to thecapacitor.